Mycotoxin production in liquid culture and on plants infected with Alternaria spp. isolated from rocket and cabbage

Phytotoxicity effect of a highly toxic isolate of Alternaria alternata metabolites from Iran

Alternaria species produce several mycotoxins, such as alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), altertoxin (ATX), tentoxin (TTX) and tenuazonic acid (TeA). This research aimed to isolate and identify mycotoxins from highly toxic Alternaria alternata (w19) and A. tennuisima isolates and their phytotoxicity effects. Fungal metabolites were extracted from 21-day cultures of Alternaria in a Czapek broth medium with the organic solvent chloroform/acetone and identified using the HPLC method. Alternaria metabolites were infiltrated in vivo into several plant leaves for phytotoxicity detection. The study investigated the impact of temperature, time, and metabolite concentration on phytotoxicity using the detached leaf infiltration technique. Five mycotoxins (TTX, TeA, ALT, AOH, and AME) were detected in A. alternata W19 isolate with 959.24, 102.03, 24.01, 9.04, and 2.44 ppm, respectively. A. tennuisima produce these toxins in a lower concentration. Infiltration of fungal metabolites induced leaf chlorosis and necrosis, which differs based on temperature, concentration and plant species. Based on our knowledge, this is the first report of Alternaria mycotoxins in Iran and a highly toxic isolate of A. alternata with rapid phytotoxicity on a wide range of susceptible hosts.

Identification and Toxicological Characterization of Alternaria japonica Strains

Fungi of the genus Alternaria are producers of biologically active compounds. Alternaria japonica is pathogenic to small radish and certain other crucifers, but has not been studied in sufficient detail. Discrepant data on its toxic metabolites are available in the literature, possibly because a limited set of nutritive substrates was used in culturing or species identification of the strains was incorrect. The objectives of this study were to accurately identify the Russian A. japonica strains and to assess the A. japonica toxigenic potential. Four Russian A. japonica strains were identified using a multifaceted approach, which included analyses of morphological characters (the diameter and morphology of colonies grown on the diagnostic media potato carrot agar (PCA) and yeast extract-glucose (YES) agar for one week), the conidial size, and the presence of chlamydospores), the nucleotide sequences of DNA markers (ITS and EF1α regions), and chemotaxonomic data (mycotoxin production). Biomass and extractive substance yields of A. japonica cultures were found to significantly depend on the composition of the liquid medium. Minor differences between the A. japonica strains were detected via metabolite profiling by HPLC/MS-UV. Extracts of A. japonica cultures exerted phytotoxic activity toward small radish leaves and cytotoxicity toward Paramecium caudatum to a level comparable with that of A. tenuissima extracts. Brassicicolin A, dihydrobrassicicolin A, and phomenins A and B, which are known for several species of the genus Alternaria, were identified in A. japonica extracts. Mycotoxins (alternariol, its methyl ether, tentoxin, tenuazonic acid, and altenuene), which are characteristic of the cosmopolitan species A. tenuissima, were not detected in cultures of the A. japonica strains. Extract toxicity and the yield of extractive substances were studied in the A. japonica strains, and strain MFP244011 proved promising as a producer of known and, presumably, new toxins upon culture on the M1D synthetic medium or semisynthetic liquid media (e.g., the Sabouraud medium).

Antimycotoxigenic Activity of Beetroot Extracts against Alternaria alternata Mycotoxins on Potato Crop

Alternaria species, mainly air-borne fungi, affect potato plants, causing black spots symptoms. Morphological identification, pathogenicity assessment, and internal transcribed spacer (ITS) molecular identification confirmed that all isolates were Alternaria alternata. The annotated sequences were deposited in GenBank under accession numbers MN592771–MN592777. HPLC analysis revealed that the fungal isolates KH3 (133,200 ng/g) and NO3 (212,000 ng/g) produced higher levels of tenuazonic acid (TeA) and alternariol monomethyl ether (AME), respectively. Beet ethanol extract (BEE) and beet methanol extract (BME) at different concentrations were used as antimycotoxins. BME decreased the production of mycotoxins by 66.99–99.79%. The highest TeA reduction rate (99.39%) was reported in the KH3 isolate with 150 µg/mL BME treatment. In comparison, the most effective AME reduction rate (99.79%) was shown in the NO3 isolate with 150 µg/mL BME treatment. In the same way, BEE application resulted in 95.60–99.91% mycotoxin reduction. The highest TeA reduction rate (99.91%) was reported in the KH3 isolate with 150 µg/mL BEE treatment, while the greatest AME reduction rate (99.68%) was shown in the Alam1 isolate with 75 µg/mL BEE treatment. GC-MS analysis showed that the main constituent in BME was the antioxidant compound 1-dodecanamine, n,n-dimethyl with a peak area of 43.75%. In contrast, oxirane, methyl- (23.22%); hexadecanoic acid, methyl ester (10.72%); and n-hexadecanoic acid (7.32%) were the main components in BEE found by GC-MS. They are probably antimicrobial molecules and have an effect on the mycotoxin in general. To our knowledge, this is the first study describing the antimycotoxigenic activity of beet extracts against A. alternata mycotoxins-contaminated potato crops in Egypt, aimed to manage and save the environment.

Development of a chemiluminescence immunoassay for detection of tenuazonic acid mycotoxin in fruit juices with a specific camel polyclonal antibody

The natural mycotoxin tenuazonic acid (TeA) in foods is identified as the most toxic mycotoxin among the over 70 kinds of secondary toxic metabolites produced by Alternaria alternata. Some hapten-antibody-mediated immunoassays have been developed for TeA detection in food samples, but these methods show unsatisfactory sensitivity and specificity. In this study, a rationally designed hapten for TeA mycotoxin generated with computer-assisted modeling was prepared to produce a highly specific camel polyclonal antibody, and an indirect competitive chemiluminescence enzyme immunoassay (icCLEIA) was established with a limit of detection of 0.2 ng mL-1 under optimized conditions. The cross-reactivity results showed that several analogs and some common mycotoxins had negligible recognition by the anti-TeA polyclonal antibody. The average recoveries spiked in fruit juices were determined to be 92.7% with an acceptable coefficient of variation, and good correlations between icCLEIA and liquid chromatography tandem mass spectrometry (LC-MS/MS) results were obtained in spiked samples. This developed icCLEIA for TeA detection with significantly improved sensitivity and satisfactory specificity is a promising alternative for environmental monitoring and food safety.

Characterization of Alternaria Species Associated with Heart Rot of Pomegranate Fruit

This study was aimed at identifying Alternaria species associated with heart rot disease of pomegranate fruit in southern Italy and characterizing their mycotoxigenic profile. A total of 42 Alternaria isolates were characterized. They were obtained from pomegranate fruits with symptoms of heart rot sampled in Apulia and Sicily and grouped into six distinct morphotypes based on macro- and microscopic features. According to multigene phylogenetic analysis, including internal transcribed spacer (ITS), translation elongation factor 1-α (EF-1α), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and a SCAR marker (OPA10-2), 38 isolates of morphotypes 1 to 5 were identified as Alternaria alternata, while isolates of morphotype 6, all from Sicily, clustered within the Alternaria arborescens species complex. In particular, isolates of morphotype 1, the most numerous, clustered with the ex-type isolate of A. alternata, proving to belong to A. alternata. No difference in pathogenicity on pomegranate fruits was found between isolates of A. alternata and A. arborescens and among A. alternata isolates of different morphotypes. The toxigenic profile of isolates varied greatly: in vitro, all 42 isolates produced tenuazonic acid and most of them other mycotoxins, including alternariol, alternariol monomethyl ether, altenuene and tentoxin.

Predicting Virulence of Fusarium Oxysporum f. sp. Cubense Based on the Production of Mycotoxin Using a Linear Regression Model

Fusarium wilt caused by Fusarium oxysporum f.sp. cubense (Foc) is one of the most destructive diseases for banana. For their risk assessment and hazard characterization, it is vital to quickly determine the virulence of Foc isolates. However, this usually takes weeks or months using banana plant assays, which demands a better approach to speed up the process with reliable results. Foc produces various mycotoxins, such as fusaric acid (FSA), beauvericin (BEA), and enniatins (ENs) to facilitate their infection. In this study, we developed a linear regression model to predict Foc virulence using the production levels of the three mycotoxins. We collected data of 40 Foc isolates from 20 vegetative compatibility groups (VCGs), including their mycotoxin profiles (LC-MS) and their plant disease index (PDI) values on Pisang Awak plantlets in greenhouse. A linear regression model was trained from the collected data using FSA, BEA and ENs as predictor variables and PDI values as the response variable. Linearity test statistics showed this model meets all linearity assumptions. We used all data to predict PDI with high fitness of the model (coefficient of determination (R² = 0.906) and adjust coefficient (R²_adj = 0.898)) indicating a strong predictive power of the model. In summary, we developed a linear regression model useful for the prediction of Foc virulence on banana plants from the quantification of mycotoxins in Foc strains, which will facilitate quick determination of virulence in newly isolated Foc emerging Fusarium wilt of banana epidemics threatening banana plantations worldwide.

Determination of Alternaria toxins in drinking water by ultra-performance liquid chromatography tandem mass spectrometry

A sensitive and reliable analytical method has been developed and validated for the determination of five Alternaria toxins, including tenuazonic acid (TeA), alternariol (AOH), alternariol monomethyl ether (AME), altenuene (ALT), and tentoxin (TEN), in drinking water using a one-step enrichment and clean-up strategy followed by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Drinking water samples were preprocessed using excess sodium sulfite to remove residual chlorine, and the pH was adjusted by formic acid. Analytes were concentrated and purified from the water samples using hydrophilic-lipophilic balanced (HLB) solid-phase extraction (SPE) cartridges. Chromatographic separation was performed on an Acquity HSS C₁₈ column using 0.1 mM ammonium carbonate and methanol as the mobile phase. The average recoveries at three spiked levels (0.1, 0.5, and 1 ng/L for TeA, AOH, and ALT; 0.01, 0.05, and 0.1 ng/L for TEN and AME) were 76.1-106.5%, with an intra-day precision less than 15.5% and inter-day precision of 11.8-16.5%. The limits of detection (LODs) were 0.05 ng/L for TeA, AOH, and ALT and 0.005 ng/L for TEN and AME. The limits of quantification (LOQs) were 0.1 ng/L for TeA, AOH, and ALT and 0.01 ng/L for TEN and AME. The developed method was applied to monitor 289 drinking water samples collected in Beijing from 2015 to 2017, and TeA and TEN were found in 28 samples, with concentrations ranging from 0.16 to 2.7 ng/L and 0.21 to 2.2 ng/L, respectively.

Contamination of fresh and dried tomato by Alternaria toxins in southern Italy

In the present investigation, fresh and dried tomato samples from markets and packinghouses located in Apulia region (southern Italy) were analysed for Alternaria toxins. All samples proved to be contaminated by tenuazonic acid (TeA); in particular, dried tomatoes were contaminated in the range 425-81,592 µg/kg, while fresh tomatoes were in the range 11-4560 µg/kg. The second most abundant toxin was alternariol monomethyl ether (AME), followed by tentoxin (TEN) and alternariol (AOH). Overall dried tomatoes were more contaminated than fresh ones, although this seemed not directly related to the presence of sodium chloride, utilized in the drying process. Five representative Alternaria isolates within those collected from samples proved to be one Alternaria arborescens (A215) and four Alternaria alternata. Within the latter species, one strain belonged to morphotype tenuissima (A216), and three to alternata (A214, A217 and A218). They were confirmed to produce TeA, AOH, and AME in vitro. This study demonstrates the possible risk for consumers' health related to the consumption of contaminated fresh and dried tomatoes, and thus the need for suitable control strategies.

Development and Application of a QuEChERS-Based Liquid Chromatography Tandem Mass Spectrometry Method to Quantitate Multi-Component Alternaria Toxins in Jujube

A simple, rapid and efficient methodology was developed and validated for the analysis of four Alternaria toxins in jujube: Tenuazonic acid, alternariol, alternariol monomethyl ether, and tentoxin. Under the optimized extraction procedure, chromatographic conditions, and instrumental parameters, the four toxins were effectively extracted via a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, and quantified by ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). Matrix-matched calibrations ranging from 0.01 to 0.5 μg mL⁻¹ were conducted for the quantification due to the matrix effect. A blank jujube sample was spiked at 40, 80 and 160 μg kg⁻¹, obtaining recoveries in the range of 83.5–109.6%. Limits of detection and limits of quantification were in the range of 0.14–0.26 and 0.47–0.87 μg kg⁻¹, respectively. Finally, the developed method was applied for the quantification of the four toxins in 14 jujube samples, including black spot-infected and uninfected samples. Results showed that the predominant toxin detected in all the samples was tenuazonic acid, the content of which was associated with the infection level; alternariol, alternariol monomethyl ether, and tentoxin were detected in all the infected samples and some of the uninfected samples with rather low contents.

Genome-Wide Analysis of Microsatellites in Alternaria arborescens and Elucidation of the Function of Polyketide Synthase (PksJ)

Microsatellites or simple sequence repeats (SSRs) have been the most widely applied class of molecular markers used in genetic studies, having applications in genetic conservation, population studies, as well as diagnostics of fungi. Mining and analysis of SSRs of the whole genome sequence have been carried out in this study for the fungus Alternaria arborescens causing early blight of tomato and well known for producing mycotoxins like alternariol (AOH), alternariol monomethyl ether (AME), etc. A total of 4097 microsatellites were identified in A. Arborescens genome. Contig 1 was identified as the most SSR-rich region which was further analyzed to correlate the presence of SSRs with different biological processes. A total of 246 putative genes were predicted in this study and KEGG pathway analysis of 155 predicted genes indicated that SSRs can be linked with important metabolic pathways, molecular functioning, signal transduction, and cellular processes. The prediction of fungal mycotoxin inducer gene Polyketide synthase (PksJ) linked with SSR in this study may be a potential candidate participating in oncogenic signal transduction in human. Our study is the first report of PksJ gene in A. arborescens, a precursor of AOH and AME.

Nonsteroidal mycotoxin alternariol is a full androgen agonist in the yeast reporter androgen bioassay

Alternariol (AOH) is a toxic metabolite of phytopathogenic fungi of the Alternaria spp. and important contaminant of agricultural commodities. According to the recent studies, AOH has a potential to modulate the endocrine system of humans and animals. In the view of these reports, our study addressed the effects of AOH on human estrogen receptor (hERα) and androgen receptor (hAR) signaling with the use of the yeast estrogen and androgen reporter bioassays. Our results show that, apart from a weak estrogenic response, AOH induces full androgenic response of the bioassay with the EC50 of 269.4μM. The androgenic potency of AOH relative to testosterone (T) is 0.046%. Moreover, in the presence of T, AOH at 5μM acts as a weak antiandrogen, whereas at higher concentrations AOH sum up with the androgenic activity of T in a dose-dependent manner, suggesting additive effect. To our knowledge it is the first report of the androgenic potency of natural, nonsteroidal substance and may have the impact on the direction of the further studies. Further research is warranted to clarify the role of AOH in disruption of AR signaling in humans and animals.

Isolation, characterization and toxicological potential of Alternaria-mycotoxins (TeA, AOH and AME) in different Alternaria species from various regions of India

Alternaria species produce various sorts of toxic metabolites during their active growth and causes severe diseases in many plants by limiting their productivity. These toxic metabolites incorporate various mycotoxins comprising of dibenzo-α-pyrone and some tetramic acid derivatives. In this study, we have screened out total 48 isolates of Alternaria from different plants belonging to different locations in India, on the basis of their pathogenic nature. Pathogenicity testing of these 48 strains on susceptible tomato variety (CO-3) showed 27.08% of the strains were highly pathogenic, 35.41% moderately pathogenic and 37.5% were less pathogenic. Phylogenetic analysis showed the presence of at least eight evolutionary cluster of the pathogen. Toxins (TeA, AOH and AME) were isolated, purified on the basis of column chromatography and TLC, and further confirmed by the HPLC-UV chromatograms using standards. The final detection of toxins was done by the LC-MS/MS analysis by their mass/charge ratio. The present study develops an approach to classify the toxicogenic effect of each of the individual mycotoxins on tomato plant and focuses their differential susceptibility to develop disease symptoms. This study represents the report of the natural occurrence and distribution of Alternaria toxins in various plants from India.

Effect of different temperatures and CO2 levels on Alternaria toxins produced on cultivated rocket, cabbage and cauliflower

Over the last 100 years, the global mean temperature has increased and has influenced several key factors that affect the occurrence and severity of fungal diseases. The effect of an increase in CO2 concentration and temperature on disease caused by four Alternaria strains and their mycotoxin production on cultivated rocket, cabbage and cauliflower plants has been investigated in this study. Six different temperature and CO2 combinations were considered: (1) 400-450 ppm CO2, 14-18 °C; (2) 800-850 ppm CO2, 14-18 °C; (3) 400-450 ppm CO2, 18-22 °C; (4) 800-850 ppm CO2, 18-22 °C; (5) 400-450 ppm CO2, 22-26 °C; and (6) 800-850 ppm CO2, 22-26 °C. Higher levels of CO2 and temperature have been found to significantly influence the disease index of the infected plants. In fact, the disease index was significantly increased at 22-26 °C and 800-850 ppm of CO2 for all of the host plants. Tenuazonic acid (TeA), alternariol, alternariol monomethyl ether and tentoxin were analysed for each climate condition using HPLC-MS/MS, and disease severity was evaluated. Higher temperature influences environmental conditions and different factors involved in plant-pathogen interaction. Temperature was the main factor involved in disease severity, while host plants and strains were found to be the factors that had the most influence on the variation of the production of mycotoxins. A large variability in the production of mycotoxins among the different host plants was observed, but TeA was always the most frequently produced mycotoxin.

Spotlight on the Underdogs-An Analysis of Underrepresented Alternaria Mycotoxins Formed Depending on Varying Substrate, Time and Temperature Conditions

Alternaria (A.) is a genus of widespread fungi capable of producing numerous, possibly health-endangering Alternaria toxins (ATs), which are usually not the focus of attention. The formation of ATs depends on the species and complex interactions of various environmental factors and is not fully understood. In this study the influence of temperature (7 °C, 25 °C), substrate (rice, wheat kernels) and incubation time (4, 7, and 14 days) on the production of thirteen ATs and three sulfoconjugated ATs by three different Alternaria isolates from the species groups A. tenuissima and A. infectoria was determined. High-performance liquid chromatography coupled with tandem mass spectrometry was used for quantification. Under nearly all conditions, tenuazonic acid was the most extensively produced toxin. At 25 °C and with increasing incubation time all toxins were formed in high amounts by the two A. tenuissima strains on both substrates with comparable mycotoxin profiles. However, for some of the toxins, stagnation or a decrease in production was observed from day 7 to 14. As opposed to the A. tenuissima strains, the A. infectoria strain only produced low amounts of ATs, but high concentrations of stemphyltoxin III. The results provide an essential insight into the quantitative in vitro AT formation under different environmental conditions, potentially transferable to different field and storage conditions.

Development and Validation of a LC-ESI-MS/MS Method for the Determination of Alternaria Toxins Alternariol, Alternariol Methyl-Ether and Tentoxin in Tomato and Tomato-Based Products

Alternaria species are capable of producing several secondary toxic metabolites in infected plants and in agricultural commodities, which play important roles in food safety. Alternaria alternata turn out to be the most frequent fungal species invading tomatoes. Alternariol (AOH), alternariol monomethyl ether (AME), and tentoxin (TEN) are some of the main Alternaria mycotoxins that can be found as contaminants in food. In this work, an analytical method based on liquid chromatography (LC) tandem mass spectrometry (MS/MS) detection for the simultaneous quantification of AOH, AME, and TEN in tomato and tomato-based products was developed. Mycotoxin analysis was performed by dispersive liquid-liquid microextraction (DLLME) combined with LC-ESI-MS/MS. Careful optimization of the MS/MS parameters was performed with an LC/MS system with the ESI interface in the positive ion mode. Mycotoxins were efficiently extracted from sample extract into a droplet of chloroform (100 µL) by DLLME technique using acetonitrile as a disperser solvent. Method validation following the Commission Decision No. 2002/657/EC was carried out by using tomato juice as a blank matrix. Limits of detection and quantitation were, respectively, in the range 0.7 and 3.5 ng/g. Recovery rates were above 80%. Relative standard deviations of repeatability (RSDr) and intermediate reproducibility (RSDR) were ≤ 9% and ≤ 15%, respectively, at levels of 25 and 50 ng/g. Five out of 30 analyzed samples resulted positive to at least one Alternaria toxin investigated. AOH was the most common Alternaria toxin found, but at levels close to LOQ (average content: 3.75 ng/g).

Characterization of Citrus-Associated Alternaria Species in Mediterranean Areas

Alternaria brown spot is one of the most important diseases of tangerines and their hybrids worldwide. Recently, outbreaks in Mediterranean areas related to susceptible cultivars, refocused attention on the disease. Twenty representatives were selected from a collection of 180 isolates of Alternaria spp. from citrus leaves and fruit. They were characterized along with reference strains of Alternaria spp. Micro- and macroscopic characteristics separated most Alternaria isolates into six morphotypes referable to A. alternata (5) and A. arborescens (1). Phylogenetic analyses, based on endopolygalacturonase (endopg) and internal transcribed spacer (ITS), confirmed this finding. Moreover, a five-gene phylogeny including two anonymous genomics regions (OPA 1-3 and OPA 2-1), and the beta-tubulin gene (ß-tub), produced a further clustering of A. alternata into three clades. This analysis suggested the existence of intra-species molecular variability. Investigated isolates showed different levels of virulence on leaves and fruit. In particular, the pathogenicity on fruit seemed to be correlated with the tissue of isolation and the clade. The toxigenic behavior of Alternaria isolates was also investigated, with tenuazonic acid (TeA) being the most abundant mycotoxin (0.2-20 mg/L). Isolates also synthesized the mycotoxins alternariol (AOH), its derivate alternariol monomethyl ether (AME), and altenuene (ALT), although to a lesser extent. AME production significantly varied among the six morphotypes. The expression of pksJ/pksH, biosynthetic genes of AOH/AME, was not correlated with actual toxin production, but it was significantly different between the two genotypes and among the four clades. Finally, ten isolates proved to express the biosynthetic genes of ACTT1 phytotoxin, and thus to be included in the Alternaria pathotype tangerine. A significant correlation between pathogenicity on leaves and ACTT1 gene expression was recorded. The latter was significantly dependent on geographical origin. The widespread occurrence of Alternaria spp. on citrus fruit and their ability to produce mycotoxins might represent a serious concern for producers and consumers.

Natural occurrence of mycotoxins and toxigenic capacity of Alternaria strains from mouldy peppers

Sweet pepper (Capsicum annuum) is an important crop cultivated worldwide, with Argentina being one of the major producers in South America. The fruit is susceptible to several fungal diseases, leading to severe economic losses for producers. In this study, Alternaria was found as the prevalent genus in mouldy peppers (50% fruits infected). Morphological identification revealed that all 64 Alternaria isolates belonged to small-spored species, most of them corresponding to A. tenuissima, A. arborescens and A. alternata species-groups. Their secondary metabolite profile was evaluated in vitro; alternariols were synthesized by most of the isolates (91% for alternariol and 92% for alternariol monomethyl ether). A high number of Alternaria spp. also produced tenuazonic acid (64%), altenuene (84%) and tentoxin (72%). In addition, damaged pepper fruits were analysed for the presence of tenuazonic acid and alternariols. A total 32 out of 48 spoiled pepper fruits were contaminated with at least one of these metabolites. Half of the samples were positive for tenuazonic acid (range 8-11,422μg/kg), while alternariol and its monomethyl ether were less frequently detected (21 and 29%, respectively) and at lower concentrations. This is the first report on the natural occurrence of Alternaria mycotoxins in Argentinean sweet pepper, and highlights a consumer risk when mouldy fruits are used in industrialized products because these compounds are not destroyed by conventional heat treatments.

Review on Mycotoxin Issues in Ruminants: Occurrence in Forages, Effects of Mycotoxin Ingestion on Health Status and Animal Performance and Practical Strategies to Counteract Their Negative Effects

Ruminant diets include cereals, protein feeds, their by-products as well as hay and grass, grass/legume, whole-crop maize, small grain or sorghum silages. Furthermore, ruminants are annually or seasonally fed with grazed forage in many parts of the World. All these forages could be contaminated by several exometabolites of mycotoxigenic fungi that increase and diversify the risk of mycotoxin exposure in ruminants compared to swine and poultry that have less varied diets. Evidence suggests the greatest exposure for ruminants to some regulated mycotoxins (aflatoxins, trichothecenes, ochratoxin A, fumonisins and zearalenone) and to many other secondary metabolites produced by different species of Alternaria spp. (e.g., AAL toxins, alternariols, tenuazonic acid or 4Z-infectopyrone), Aspergillus flavus (e.g., kojic acid, cyclopiazonic acid or β-nitropropionic acid), Aspergillus fuminatus (e.g., gliotoxin, agroclavine, festuclavines or fumagillin), Penicillium roqueforti and P. paneum (e.g., mycophenolic acid, roquefortines, PR toxin or marcfortines) or Monascus ruber (citrinin and monacolins) could be mainly related to forage contamination. This review includes the knowledge of mycotoxin occurrence reported in the last 15 years, with special emphasis on mycotoxins detected in forages, and animal toxicological issues due to their ingestion. Strategies for preventing the problem of mycotoxin feed contamination under farm conditions are discussed.